Phonetically, the IPA transcription of [처] and [치어] is [ʨʰʌ] and [ʨʰi.ʌ]. Their phonetical difference is the number of syllables and the presence of [i]. But what is the phonological difference?
Being a palatal consonant, we can say [ʨʰ] has dorsal position of [i]. So the phonological difference is the duration of [i].
How long is the duration that makes a boundary between [처] and [치어]? Is there an intermediacy so the speech can be transcribed as [쳐]?
EDIT: Does the same way of discrimination apply between [치어] and [치여]?